Alarm system

ABSTRACT

A photocell-activated intruder alarm system, including a control circuit adapted to automatically adjust system operation to ambient light conditions and adapted to facilitate bore sighting of the apparatus on an external light source. A time delay inherently present in said circuit provides delay in arming of the alarm after activation of the system, whereby a user may remove himself from the protected area without discharging the alarm.

1 States Patent Sept. 18, 1973' 1 ALARM SYSTEM 7 [76] Inventor: Josh B.Taggart, Box 366, Rt.'5,

Bristol, Tenn. 37620 [22] Filed: Nov. 17, 1970 [21] v Appl. No.: 90,338

[56] References Cited UNITED STATES PATENTS 3,636,532 l/l972 Apple340/258 B 3,329,946 Robbins 340/258 B 3,189,883 6/1965 Lucas et al...340/258 B 3,585,621

6/1971 DiCello 340/237 S Primary ExaminerDavid L. Trafton Attorney-FrankP. Cyr

[57] ABSTRACT A photocell-activated intruder alarm system, including acontrol circuit adapted to automatically adjust system operation toambient light conditions and adapted to facilitate bore sighting of theapparatus on an external light source. A time delay inherently presentin said circuit provides delay in arming of the alarm after activationof the system, whereby a user may remove himself from the protected areawithout discharging the alarm.

8 Claims, 4 Drawing Figures I 2 a Z 1a v '51 LIGHT SENSOREXTElggslcllGHT 5 BORE SIGHT INDICATOR 2/ STANDBY POWER 27 l SMOKE/HEATCONTROL UNIT I JUNCTION DETECTOR AND BOX 2 MODE SELECTOR EXTERNAL 25 l 9V ALARM LINE POWER 4 23 POWER TRANSFORMER I INTERNAL ALARM I L I0 JAUXILIARY LIGHT SENSOR Patented Sept. 18, 1973 2 Sheets-Sheet l 1055mmwoo:

e rmQEuEE I N VEN '1 OR. B TAGGART A TTORNE V 2 Sheets-Sheet z PatentedSept. 18, 1973 E OUT THRESHOLD QUESCENT VALUE 0.5

POTNT OF LIGHT TIME INTERCEPTION FIG. 4 E OUT 05 0V APPLICATION OF LIGHT52 IN 'E.\"i 0R JOSH B. TAGGART ATTORNEY DEVICE FOR SUPPORTING SHEETMATERIALS The present invention relates to a device for supporting aload of sheets thereon, more particularly, to such a device wherein thesheets are positioned edgewise on a supporting surface and lean againstan upright wall and the device is positionable in a vertical orrearwardly inclined position.

In the production of flat glass, various forms of load supportingdevices have been used to hold the unit loads of glass sheets as theycome from the production line. Similar or other forms of load supportingdevices have been used for holding such loads of glass sheets inwarehouses during storage or in vehicles during transportation. Suchdevices have also been provided with wheels to facilitate the movementof loads of sheets over relatively short distances, such as from theproduction plant to a shipping dock or a warehouse. Since such devicesare generally provided with raised load supporting surfaces they can belifted or carried with their loads in place by fork lift trucks or otherhandling apparatus so that it is not essential that the devices bealways equipped with wheels.

These supporting devices are generally loaded by individually carryingeach sheet over the front edge of the supporting surface and releasingthe sheet so that its face leans against a wall extending upwardly fromthe rear portion of the load supporting surface. Each subsequentlyloaded sheet thus rests against the face of the previously loaded sheet.Unloading of this device is accomplished by the reverse sequence of theabove operation. The loading and unloading operations thus require thatthe front of the supporting device be unobstructed by any load retainingwall or other structure. Basically, the supporting devices comprise araised load supporting deck or surface and a rear wall upstanding fromthe rear portion of the supporting deck :so that when the device isviewed from the end thereof the supporting surface and wall define asubstantially L-shaped structure.

During the loading and unloading operation the sheets which may be onthe device at any given time must be stably supported. Since it isundesirable to provide any form of retaining structure on the frontportion of the supporting device it is generally provided that theupstanding wall is inclined rearwardly and the sheets are leaned againstthis inclined wall. Such a structure is relatively inefiicient becausethe volume of storage space required for accommodating a storage deviceis disproportionate with respect to its load bearing capacity. When itis necessary to accommodate a large number of supporting devices loadedwith sheets, the inefficiently used storage space increases directly inproportion to the number of devices being stored.

It is therefore the principal object of the present invention to providea novel and improved device for supporting a load of sheets andrequiring a minimum of storage area.

It is another object of the present invention to provide a supportingdevice for sheet material which enables sheets of glass and othermaterial to be economically and efficiently stored, handled andtransported.

It is a further object of the present invention to provide a device forsupporting a load of sheets thereon in vertical position and upon whichthe sheets may be efi'b ciently loaded or unloaded.

According to one aspect of the present invention, the device forsupporting a load of sheets may comprise supporting surface means havingfront and rear leg means. Wall means are upstanding from the rearportion of the load supporting surface means so as to support a load ofsheets placed edgewise on the supporting surface and leaning against thewall means. The rear leg means comprises movable rear leg meanspivotally mounted on the supporting device to pivot between a positionin which the wall means is substantially vertical and another positionin which the wall means is inclined rearwardly from the bottom to thetop thereof.

The supporting surface means and the wall means essentially define anL-shaped structure and a movable leg or legs may be pivotally mountedfrom a point on the wall means above the supporting surfaces. A catchmember is pivotally mounted on the device and locks the movable rear legin a position wherein the supporting device is inclined. The catchmember can be pivoted to a vertical position in which it is inoperativeto enable the movable rear leg to be pivoted to a position in which thesupporting device is substantially vertical. A retaining member may beprovided to pass over and in front of the load of sheets and bedetachably connected to the upper portion of the wall means and/or tothe front portion of the supporting surface means.

The movable rear leg may also be pivoted to the lower portion of thesupporting device so that when the device is in the inclined positionthe rear portion of the device will be supported at the junction of thesupporting surface and upstanding wall means.

The supporting device of the present invention is particularlyadvantageous since during loading the device can be positioned with itsrear wall inclined and the loaded device can then be stored in avertical position in which it occupies a considerably smaller space. Thefloor space occupied by a loaded device in a vertical position is up to45% less than for other known storage devices. Accordingly, the givenarea of a storage room, a transport container or vehicle can hold aconsiderably greater number of loaded devices of the present inventionthan previously known sheet supporting devices. It is apparent thatwhile the rear wall of the storage device should be inclined duringloading and unloading operations it is not necessary that the wall beinclined when the device has been loaded and is being stored ortransported. At these times when the supporting device is in a verticalposition the load is retained in position by suitable retaining strapsor bars.

Other objects and advantages of the present invention will be apparentupon reference to the accompanying description when taken in conjunctionwith the following drawings, which are'exemplary, wherein;

FIG. 1 is an overall perspective device according to the presentinvention and looking at the rear thereof;

FIG. 2 is a perspective view but in enlarged scale showing details ofthe construction of the catch member on the supporting device of FIG. 1;

FIG. 3 is a side elevational view of a modified supporting device; and

FIG. 4 is a side elevational view of a portion of still anothermodification of the load supporting device according to the presentinvention.

Proceeding next to the drawings wherein like reference symbols indicatethe same parts throughout the various views, a specific embodiment andmodifica- As seen therein a control module 2 forms the heart of thesystem and includes generally a control unit and mode selector means 4,bore sight indicator 6, light sensor means 8, and internal alarm 10.Control module 2 will typically comprise a single compact unit, and assuch unit will commonly be positioned in an area such as a room of adwelling place desired to be protected. The module 2 is preferablyhoused in an attractive case or the like which blends in well with thesurrounding environment.

Control unit and mode selector means 4, which will hereinafter bedescribed in greater detail, performs the various control functions forthe system and also includes switching means for powering the system andarming the alarm. Electrical power for module 2 is shown as being fed tomeans 4 by a line 25. Such power originates as line power at 12 and isstepped down in voltage at transformer 14 so that all potentials withinthe system are relatively low and therefore safe for the user.Transformer 14 is shown in the Figure as a separate unit external tomodule 2 but it will of course be clear that such element could as wellbe contained within module 2 itself. Similar considerations apply to thestandby power unit 14. This unit, which is seen to be in communicationwith means 2 via the lines 27 and 29, may simply comprise a battery packor the like and furnishes power to means 4 by line 29 in the event ofline power failure. The unit 16 is thus shown as residing external tomodule 2 but again could clearly be merged into the basic module 2 if sodesired.

Control unit and mode selector means 4 is seen to be provided with aninput via line 31 from light sensor 8. The latter, which may be aconventional photocell or the like, is, in accordance with the inventionsighted upon a remote external light source 18. Source 18, further inaccordance with the invention, may be any convenient illuminatingsource, including for example, a common room lamp, a reflecting surface,or a window accessible to external daylight. Source 18 will typically beconsiderably. removed from sensor 8 e.g., by being placed at theopposite side of a protected room. Sighting of sensor 8 upon sourcel8'is accomplished by physically manipulating module 2 to yeildappropriate indication in bore sight indicator 6 (connected to means 4)that optimal sighting has been achieved. The precise manner in whichthis action occurs will be set forth subsequently. Let it suffice forpresent to point out that after means 4 has appropriately been set forbore sighting, indicator 6 which may be a meter or light--- is observedas the orientation of module 2 is varied, the circuit of means 4 beingsuch as to effect responses at indicator 6 which can be analyzed todetermine the accuracy of sighting.

Once the sensor 8 of module 2 is thus accurately sighted on source 18,control unit and mode selector means 4 is adjusted to the "arm" mode,and thereafter fluctuations in light intensity falling upon sensor 8which are of the type caused by an intruder passing between sensor 8 andsource 18 will be detected at means 4 which will in turn activateinternal alarm 10.

While the elements thus far described are capable of operating as asystem without additional detection devices, the system will typicallyinclude additional sensors such as auxiliary light sensor 19, andsmoke/heat detector 21. Sensor 19 may thus be used in the precise mannerdescribed in connection with sensor 8 to protect additional areaspossibly remote from the area where module 2 is located, the auxiliarysensor being connected to module 2 at means 4 by the line 33. Obviouslya plurality of such sensors may, if desired, be so employed. Similarly asmoke/heat detector 21 which may be of any conventional design may beconnected back to module 2, and provide signals thereto indicative ofdangerous heat or smoke conditions, such signals serving ultimately toactivate alarm 10. In order to add flexibility to the system, smoke/heatdetector 21 which may be one of a plurality of such units will typicallybe joined to module 2 by a junction box 19 which has connection meansfor a plurality of such detectors. Such box 20 may also serve as aconnecting link between means 4 and an external alarm 23. The externalalarm 23 will typically be conspicuously mounted outside a building orthe like and may be activated commonly with or independent of internalalarm 10.

FIG. 2 is a simplified schematic electrical diagram for the controlmodule portion of the system. Switching means for activating thiscircuit and switching its output and input to the various detectors andalarms etc. of FIG. 1, are for purposes of simplicity not shown, but areconventional, such switching being activated in accordance with thedesired mode of operation of the system.

As seen in FIG. 2 a closed loop circuit is provided consisting of a DC.differential amplifier (transistors 20 and 22), a DC. amplifier(transistor 28),.and an emitter follower (transistor 24). Transistor 26serves as a DC. amplifier to provide a large signal to resistor 30. Thelatter, while shown for purposes of the present diagram as a resistor,actually corresponds to bore sight indicator 6 of FIG. 1 and may inpractice comprise a light bulb or a current measuring meter.

The photocell 36 of FIG. 2 corresponds to light sensor 8 of FIG. 1.Resistor 38 and capacitor 40 form a long time constant with respect tothe transient signal to be sensed 'via photocell 36, thus keeping theclosed loop from cancelling the desired signal.

Due to the fixed voltage applied to the base of transistor 22, thevoltage across resistor '50 will remain approximately constant whenevertransistor 22 is conducting. (It will be noted that transistor 22 willalways be conducting when the loop stabilizes, since it is the onlysource of current for the base of transistor 28.) Thus we can write:

where E, is the supply voltage for the circuit.

At turn-on, capacitor 40 is discharged; thus the voltage at the junctionof resistors 42 and 44 will be at or near ground. The value of resistor42 is made sufficiently small to force all the current throughtransistor 20 under these conditions, so that With transistor 22 off,transistor 28 is also off and capacitor 40 starts to charge toward Ethrough resistors 38 and 46. Emitter follower 24 prevents loading of thetime constant and transfers the voltage on capacitor 40 so that V, E V0.5. (where V voltage at junction of resistors 42 & 44.);

where V is the voltage on capacitor 40.

As V increases in value, the voltage drop across resistor 42 in parallelwith the photocell is slowly reduced, decreasing i (the base current oftransistor 20) until i multiplied by the D.C. current gain of transistor20 (h,, is less than K At this point transister 22 starts to conduct,increasing until transistor 28 conducts, reducing the voltage at thecollector of transistor 28 until capacitor 40 ceases to charge. The loopstabilizes at this point.

As light impinges on photocell 36, the resistance of this devicedecreases, becoming muchsmaller in value than resister 42. Thismomentarily increases i decreasing l cutting off transistor 28, allowingcapacitor 40 to charge further and stabilize at a higher value. Afterrestabilization and I both return to essentially their initial values.

Resistor 48 is of such value that the drop across it is small comparedto the base-to-emitter drop of transistor 28. Thus the output underquiescent conditions will be approximately 0.5 volts under a very widerange of resistance values for photocell 36, in consequence of which thecircuit is self-adjusting for a corresponding wide range of ambientlighting conditions. When the light to photocell 36 is interrupted thevalue of is reduced and l is increased by this b xhfa of transistor 20.This produces a positive signal at the 'circuit output 32 of. amagnitude in voltage dependent on the value of load resistor 34(corresponding e.g., to

alarm resistor 48 and K If thelight is permanently interrupted theoutput E will slowly decay to its original value as shown in FIG. 3.

By setting a threshold level for activation, any number of devices,(such as an alarm, a relay,.a counter, a computer input, etc.) can beactivated by the said output. It is also noted that by applying a f xedvoltage other than zero to the emitter of transistor 28and to the bottomof resistor 34, the quiescent value can be varied over a range ofvalues, including a negative value. Thus the present device can be setso that it is compatible with external devices with various trigger orthreshold levels.

It is noted that the circuit ofFlG. 2 will sense sudden increases inlight intensity as well as decreases. The output for a step increase isthus just the opposite in polarity, as shown in FIG. 4. This feature isutilized in bore sighting. In particular as a highly directional lightcell is pointed toward a light source, the sudden negative swing at theoutput --as shown in FIG. 4- cuts off transistor 28. The only currentthen flowing through the base of transistor 26 is the capacitor 40charge current via resistors 38and 46. Since resistor 38 is much largerthan resistor 46, this current is too small to light delay in arming ofthe alarm following activation of this mode of system operation, mayalso be appreciated from the graph of FIG. 4. In particular, it will beobserved therein that a considerable time period is present between apoint such as 52 where E has dropped 'to zero and the point wherequiescent voltage is attained. This same period is, of course, presentfollowing initial arming, and serves admirably to enable the system userto remove himself from presence of the photocell without effectingdischarge of the alarm.

While the present invention has been particularly set forth in terms ofspecific embodiments thereof, it will be appreciated in view of theinstant disclosure, that numerous variations upon the teaching are nowenabled, which variations are yet within the true scope of thisteaching. Accordingly, the invention is to be broadly construed andlimited only by the scope and spirit of the claims now appended hereto.

' Iclaim:

.]l. A light sensor-activated intruder alarm system, comprising: 3

' a. light sensor means sightable on a spaced light source;

b. a control unit connected to receive the output from said light sensormeans, said unit including means for providing a signal output at arelatively fixed quiescent level in the presence'of slow light changesat said sensor and at levels detectably removed from said quiescentlevel in the presence of transient light changes at said sensor, saidmeans comprising a self-stabilizing DC closed loop circuit in serieswith said sensor, said loop including amplifier means and having arelatively long time constant with respect to said transient signals,but not with respect to said slow light changes sought to becompensated; r bore. sight detector means connected tosaid signal output.of said loop, said means being adapted to provide indication of suddenincreases in light at said sensor, whereby sighting of said sensor onsaid light source may be detected; and I d. alarm means connected tosaid signal output, said means being adapted to provide indicationofsudden decreases in light at said sensor, whereby intrusion between saidsensor and said light source may 'be detected.

2. Apparatus in accordance with claim 1, wherein said bore' sightdetection means comprises an indicator lamp and D.C. amplifier means forreceiving said signal output and providing power to said lamp inaccordance with said signal output.

3. Apparatus in accordance with claim 1 wherein said sensor comprises aphotocell, the resistance of which varies in response to the incidentlight level and wherein said loop includes differential amplifier means,the output from one side of said photocell being .one input to saiddifferential amplifier means, and the output from said differentialamplifier means being provided in series to the other side of saidphotocell for feeding back in said loop.

4. Apparatus in accordance with claim 3, wherein said control unitincludes power switching means and means for switching said system to anarm mode, said RC circuit means having a sufficient time constant toprovide upon switching to said arm mode a sufficient delay in saidsignal output attaining said quiescent level to permit the systemoperator to remove himself from the intruder detection zone of saidsystem.

5. Apparatus in accordance with claim 1 including a plurality of lightsensors.

6. Apparatus in accordance with claim 5 including a plurality of saidalarm means, at least one of said means ferential amplifier means backto said sensor.

1. A light sensor-activated intruder alarm system, comprising: a. lightsensor means sightable on a spaced light source; b. a control unitconnected to receive the output from said light sensor means, said unitincluding means for providing a signal output at a relatively fixedquiescent level in the presence of slow light changes at said sensor andat levels detectably removed from said quiescent level in the presenceof transient light changes at said sensor, said means comprising aself-stabilizing DC closed loop circuit in series with said sensor, saidloop including amplifier means and having a relatively long timeconstant with respect to said transient signals, but not with respect tosaid slow light changes sought to be compensated; c. bore sight detectormeans connected to said signal output of said loop, said means beingadapted to provide indication of sudden incReases in light at saidsensor, whereby sighting of said sensor on said light source may bedetected; and d. alarm means connected to said signal output, said meansbeing adapted to provide indication of sudden decreases in light at saidsensor, whereby intrusion between said sensor and said light source maybe detected.
 2. Apparatus in accordance with claim 1, wherein said boresight detection means comprises an indicator lamp and D.C. amplifiermeans for receiving said signal output and providing power to said lampin accordance with said signal output.
 3. Apparatus in accordance withclaim 1 wherein said sensor comprises a photocell, the resistance ofwhich varies in response to the incident light level and wherein saidloop includes differential amplifier means, the output from one side ofsaid photocell being one input to said differential amplifier means, andthe output from said differential amplifier means being provided inseries to the other side of said photocell for feeding back in saidloop.
 4. Apparatus in accordance with claim 3, wherein said control unitincludes power switching means and means for switching said system to anarm mode, said RC circuit means having a sufficient time constant toprovide upon switching to said arm mode a sufficient delay in saidsignal output attaining said quiescent level to permit the systemoperator to remove himself from the intruder detection zone of saidsystem.
 5. Apparatus in accordance with claim 1 including a plurality oflight sensors.
 6. Apparatus in accordance with claim 5 including aplurality of said alarm means, at least one of said means together withsaid control unit, bore sight indicator, and at least one of said lightsensors being contained within a compact module.
 7. Apparatus inaccordance with claim 6, further including smoke/heat detector meansconnected to said control unit, said control unit further includingmeans adapted to discharge at least one of said alarm means upon receiptof a signal from said detector means indicative of smoke or heat. 8.Apparatus in accordance with claim 3, wherein an emitter follower and RCcircuit means couples said differential amplifier means back to saidsensor.